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J/ApJ/459/606 Distances of planetary nebulae (Schneider+ 1996)
The distances of planetary nebulae and the galactic bulge
Schneider S.E., Buckley D.
<Astrophys. J. 459, 606 (1996)>
=1996ApJ...459..606S (SIMBAD/NED BibCode)
ADC_Keywords: Planetary nebulae ; Morphology ; Radio lines
Keywords: circumstellar matter - Galaxy: center - planetary nebulae: general -
radio continuum: ISM
Abstract:
We describe an improved method for determining the distances of
planetary nebulae (PNe) based on a theoretical/empirical relationship
between their radii and radio surface brightness. Like the Shklovsky
(constant mass) distance method, our relationship requires only radio
flux density and angular size measurements, which are widely available
in the literature. Based on models matching the overall Galactic
distribution of PNe, we determine how PNe observed in the direction of
the Galactic center are actually distributed relative to the bulge in
order to establish the usefulness of these PNe for distance studies.
We then use the bulge PNe along with PNe with independent distances to
establish, calibrate, and test the accuracy of the method. When
compared to the best available data our distance method appears to
yield distance errors consistent with a scatter of <25% (1σ).
And, based on our models scaled to local PNe, we find a mean Galactic
center distance of 8.3±2.6kpc for the bulge PNe. The relationship
that PNe exhibit between radius and surface brightness is in excellent
agreement with our simulated nebulae from Paper I (Buckley &
Schneider, 1995ApJ...446..279B). We find that no simple power law can
describe the changing mass and radius of a PN as it ages; however, our
empirical relationship has a limiting behavior that is almost
indistinguishable from the assumption made in Shklovsky's distance
method that PNe have a constant ionized mass. We reexamine the dispute
about the validity of the Shklovsky's distance method as applied to
Galactic center PNe in light of these results, and we argue that the
Shklovsky method does predict the distances of large, low surface
brightness PNe well, but it increasingly overestimates the distance of
smaller PNe.
File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file
table1 42 189 Radio flux densities and sizes of Galactic Center PNe
See also:
V/84 : Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker+, 1992)
Byte-by-byte Description of file: table1
Bytes Format Units Label Explanations
1- 10 A10 --- PN PN designation
12- 17 F6.1 mJy S6cm ? Flux density at 6cm (5GHz)
19 A1 --- l_Diamph Limit flag on Diamph
20- 23 F4.1 arcsec Diamph ? Photographic diameter from the
Strasbourg-ESO catalogue (Cat. V/84)
24 A1 --- u_Diamph Uncertainty flag on Diamph
25 A1 --- n_Diamph [s)] Note on Diamph (1)
27 A1 --- l_Diam Limit flag on Diam
28- 32 F5.2 arcsec Diam ? Adopted "metric" diameter
33 A1 --- n_Diam [)] Note on Diam (1)Note (1): s: stellar
): indicates that the source shows significant discrepancies between
radio and photographic measurements
History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 10-Apr-1997